Abstract:

Objective To investigate the phenomenon,reason and parentage index calculation of unsure mutation source in STR loci in paternity testing. Methods Chelex-100 method was used to extract DNA from 4 385 family samples. The allele genotyping of STR loci was analyzed by capillary electrophoresis after amplification with polymerase chain reaction（PCR）. Mutated STR loci were verified by Identifiler system or Microreader 23sp ID system,respectively,and then validated by locus-specific primer amplification and sequencing. Results Mutations of unsure source were found in D12S391,TPOX and D8S1179 loci in two families. The authenticity of the mutation occurrence was confirmed by different detection systems. Sequencing results showed that the mutations of D12S391 and TPOX loci came from their mother,and both were one-step mutations. Conclusion Mutations of unknown source of STR locus has great influence on the calculation of the parentage indexand the identification conclusion. For mutations of unknown source,primers should be designed for amplification and sequencing to verify the source. The parentage index should be calculated correctly to ensure the accuracy and scientificity of the identification conclusion.

Key words: Paternity testing, Unknown source mutation, D12S391 locus, TPOX locus